Botan::AffinePointTable< C, R > Class Template Reference

#include <pcurves_mul.h>

Public Types
using	AffinePoint = typename C::AffinePoint
using	ProjectivePoint = typename C::ProjectivePoint
using	WordType = typename C::WordType

Public Member Functions
	AffinePointTable (std::span< const ProjectivePoint > pts)
AffinePoint	ct_select (size_t idx) const
AffinePoint	ct_select (size_t idx, size_t iter) const

Static Public Attributes
static constexpr bool	WholeRangeSearch = (R == 0)

Detailed Description

template<typename C, size_t R = 0>
class Botan::AffinePointTable< C, R >

A precomputed table of affine points with constant time lookup

If R is zero then the entire table is scanned for each lookup.

If R is not zero, then the table must be a multiple of R points long. Each lookup will be examine a range of length R, as in pts[0..R], pts[R..2*R], ...

Definition at line 38 of file pcurves_mul.h.

Member Typedef Documentation

AffinePoint

template<typename C, size_t R = 0>

using Botan::AffinePointTable< C, R >::AffinePoint = typename C::AffinePoint

Definition at line 40 of file pcurves_mul.h.

ProjectivePoint

template<typename C, size_t R = 0>

using Botan::AffinePointTable< C, R >::ProjectivePoint = typename C::ProjectivePoint

Definition at line 41 of file pcurves_mul.h.

WordType

template<typename C, size_t R = 0>

using Botan::AffinePointTable< C, R >::WordType = typename C::WordType

Definition at line 42 of file pcurves_mul.h.

Constructor & Destructor Documentation

AffinePointTable()

template<typename C, size_t R = 0>

Botan::AffinePointTable< C, R >::AffinePointTable ( std::span< const ProjectivePoint > pts )

inlineexplicit

Definition at line 46 of file pcurves_mul.h.

                                                                    {
         BOTAN_ASSERT_NOMSG(pts.size() > 1);
 
         if constexpr(R > 0) {
            BOTAN_ASSERT_NOMSG(pts.size() % R == 0);
         }
 
         // TODO scatter/gather with SIMD lookup
         m_table = to_affine_batch<C>(pts);
      }

References BOTAN_ASSERT_NOMSG, and Botan::to_affine_batch().

Member Function Documentation

ct_select() [1/2]

template<typename C, size_t R = 0>

AffinePoint Botan::AffinePointTable< C, R >::ct_select ( size_t idx ) const

inline

If idx is zero then return the identity element. Otherwise return pts[idx - 1]

Definition at line 60 of file pcurves_mul.h.

      {
         BOTAN_DEBUG_ASSERT(idx < m_table.size() + 1);
 
         auto result = AffinePoint::identity(m_table[0]);
 
         // Intentionally wrapping; set to maximum size_t if idx == 0
         const size_t idx1 = static_cast<size_t>(idx - 1);
         for(size_t i = 0; i != m_table.size(); ++i) {
            const auto found = CT::Mask<size_t>::is_equal(idx1, i).as_choice();
            result.conditional_assign(found, m_table[i]);
         }
 
         return result;
      }

References BOTAN_DEBUG_ASSERT, Botan::CT::Mask< T >::is_equal(), and WholeRangeSearch.

Referenced by Botan::mul2_exec(), and Botan::varpoint_exec().

ct_select() [2/2]

template<typename C, size_t R = 0>

AffinePoint Botan::AffinePointTable< C, R >::ct_select ( size_t idx, size_t iter ) const

inline

If idx is zero then return the identity element. Otherwise return pts[idx - 1] out of the table subrange pts[iter*R..(iter+1)*R]

Definition at line 81 of file pcurves_mul.h.

      {
         BOTAN_DEBUG_ASSERT(idx < R + 1);
         BOTAN_DEBUG_ASSERT(R * (iter + 1) <= m_table.size());
 
         auto result = AffinePoint::identity(m_table[R * iter]);
 
         // Intentionally wrapping; set to maximum size_t if idx == 0
         const size_t idx1 = static_cast<size_t>(idx - 1);
         for(size_t i = 0; i != R; ++i) {
            const auto found = CT::Mask<size_t>::is_equal(idx1, i).as_choice();
            result.conditional_assign(found, m_table[R * iter + i]);
         }
 
         return result;
      }

References BOTAN_DEBUG_ASSERT, Botan::CT::Mask< T >::is_equal(), and WholeRangeSearch.

Member Data Documentation

WholeRangeSearch

template<typename C, size_t R = 0>

bool Botan::AffinePointTable< C, R >::WholeRangeSearch = (R == 0)

staticconstexpr

Definition at line 44 of file pcurves_mul.h.

Referenced by ct_select(), and ct_select().

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The documentation for this class was generated from the following file:

• src/lib/math/pcurves/pcurves_mul.h